Our goal is to gain a better understanding of the mechanism of protein biosynthesis, and study the role of the different factors required for the translation of messenger RNA. The conventional cell-free system of E. coli is quite complex, and its many components have not been sufficiently characterized. We will continue to examine the chemical and physical properties of chain initiation factors 2 and 3, and ribosomal protein S1 in order to clarify their respective roles in the recognition of initiator tRNA, mRNA, and ribosomes. Specifically, we would like to determine whether the site of action of IF-3 is solely at the level of 30S ribosomal subunits, or whether the factor can act on the 70S ribosome. The role of ribosomal protein S1 in the process of IF-3 attachment will also be investigated. During embryonic development of Artemia salina, encysted gastrulae are produced which undergo desiccation. In such cysts, protein synthesis and development stop, and after rehydration, metabolism is resumed. The encysted gastrulae eventually differentiate into partially formed nauplii larvae which emerge from the cysts. We will examine any modification of the protein synthesis machinery during the embryological development of Artemia salina. Emphasis will be on the changes in polypeptide chain initiation factors and messenger RNAs. The effect of these changes on the control of protein synthesis during embryological cellular differentiation will be determined.